Automotive beam spring

ABSTRACT

A beam spring capable of substantial elastic deformation in two planes to provide for independent wheel suspension and to commonize suspension mounting systems in a vehicle chassis.

CROSS REFERENCE TO RELATED APPLICATION

The present application is related to co-pending application Serial No.V201-0413, entitled “Automotive Independent Suspension System Using aBeam Spring”, which is being concurrently filed herewith and which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to vehicle suspension springs,and more particularly to generally longitudinal, non-convoluteautomotive beam springs used to provide spring action in two planes.

2. Description of the Related Art

Previous automotive suspension systems using leaf springs relied onsubstantial elastic deformation in only one plane. Substantialinboard-outboard deformation of the spring was controlled bysubstantially higher spring rate stiffness in these planes created bywide leaf spring cross sections. Inboard-outboard deformation wastypically not desired in these configurations since they were mainlypaired with conventional beam axles which spanned the width of thevehicle and whose weight was completely unsprung by the suspension thatis the entire weight of the axle was attached to the spring and notdependent on the chassis.

The conventional leaf spring designs are excellent for beam axleapplications. Conventional Leaf springs are not suited to independentsuspension systems however. These independent suspension systems arecharacterized by axles with a differential attached to the chassis anduse articulated halfshafts to transmit torque to the unsprung wheelends. The wheel ends in an independent suspension system travel in anarc controlled by a control arm. Since these independently suspendedwheel ends travel in an arc rather than straight up and down (requiringtwo planes of deformation), leaf springs with only one plane of elasticdeformation are not suitable. Currently, these independent suspensionsystems rely on coil springs and control arms to provide a suitablesuspension. Coil springs mount differently on a chassis than do leafsprings and so the two systems are not interchangeable on a commonchassis. In addition, control arms for coil spring suspensions are oftenvery heavy and rely on multiple attachment points and expensive bushingsto provide appropriate suspension characteristics. Coil springs andtheir control arms thus introduce added complexity and cost to anautomobile over a conventional leaf spring design.

It would be desirable, therefore, to provide a spring which mounts to avehicle like a leaf spring yet provides the multiple-plane elasticdeformation of a coil spring.

BRIEF SUMMARY OF THE INVENTION

The present invention overcomes the disadvantages of the prior artapproaches by providing a beam spring, which substantially elasticallydeforms in two planes.

It is an object and advantage of this invention to provide a beam springwith a longitudinal axis substantially greater in length than thehorizontal and vertical axes and which is capable of substantialrelative elastic deformation in both the vertical and horizontal planes.

These and other advantages, features and objects of the invention willbecome apparent from the drawings, detailed description and claims whichfollow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a typical leaf spring suspensioncombined with a beam axle.

FIG. 2 is a perspective view of a beam spring with vertical andhorizontal spring rates controlled by the cross section of the beamspring.

FIG. 3 is a perspective view of a beam spring with distinct crosssectional sizes and shapes at different longitudinal positions along thebeam spring

FIG. 4 is a perspective view of a beam spring with a supplementalstiffener.

FIG. 5 is a perspective view of a beam spring with a supplementalstiffener which has distinct cross-sectional sizes at differentlongitudinal positions along the beam spring.

FIG. 6 is a perspective view of a beam spring attached to a chassis attwo points.

FIG. 7 is a perspective view of a beam spring attached to a chassis atone point.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Referring now to the drawings, FIG. 1 shows a conventional leaf springsuspension. A leaf spring 10, is mounted to a chassis 20 with a shackle30 and a bushing 32. This mounting configuration, when combined with thecross sectional stiffness characteristics of the wide leaf spring 10,insures that this suspension elastically deforms in a substantial manneronly in the vertical plane 40.

FIG. 2 shows an automotive beam spring 50 comprising a spring length 60,a longitudinal centerline 70, and an outer surface 80, said outersurface defined by at least one spring cross section 90, wherein said atleast one spring cross section is perpendicular to said longitudinalcenterline, said at least one spring cross section further comprising amaximum cross section width 100, wherein the ratio of said spring lengthto said maximum cross section width is at least 2. The spring rates inthe vertical plane 40 and the horizontal plane 110 are bothsubstantially greater than in relation to the spring rate in thelongitudinal plane 120.

FIG. 3 shows an automotive beam spring 50 with multiple cross sections,i.e., distinctly varying size or shape of the transverse cross sectionat different longitudinal positions along beam spring 50. These crosssections impart a unique spring rate in the horizontal and verticalplanes. In this beam spring, the variation of the spring rates in thevertical plane 40 and the horizontal plane 110 may be due strictly tothe variances in the cross section or may be due to the variances of thecross section and variances in material properties throughout ahomogenous or semi-homogenous material. Variances in material propertiesin a homogenous material may be the result of heat or chemical treatingof various areas of the material. The spring rates in the vertical plane40 and the horizontal plane 110 are both substantially greater than thespring rate in the longitudinal plane 120. The invention includes theuse of varied, controlled rates of stiffness along various axesthroughout the beam spring in order to tune the stiffness response ofthe beam spring in the several planes in which it must elasticallydeform. There are many ways of varying the stiffness rates of springsalong various axes throughout the spring. As in FIG. 3 the crosssectional widths of the beam spring in various axes transverse to itslongitudinal centerline are varied to provide a varying stiffnessresponse of the beam spring in the multiple planes in which it mustelastically deform. Specific embodiments include using circular crosssections at the beam spring ends compared to a middle cross section thatis rectangular—substantially wider in the horizontal plane than in thevertical plane. Another embodiment employs rectangular cross sections ofvarious sizes as in FIG. 3. This configuration offers relative highstiffness horizontally at the midsection but allows horizontal elasticdeformation to be concentrated at the ends, where it is easier tocontrol the deformation movement in the horizontal plane, without unduevibration or ‘wag’. Alternately, one may want to employ wide, flat crosssections at the ends to promote durability, while using a smaller, roundmidsection for elastic deformation in the horizontal plane. Other crosssections may be used in multiple combinations to tune the response ofthe suspension—for instance progressively increasing spring rates may bedeveloped by increasing the stiffness of the beam spring along itslength by varying the cross section.

FIG. 4 shows a beam spring 50 with a supplemental stiffener 140. Becausethe supplemental stiffener 140 is made up of either softer or hardermaterial than the rest of the beam spring, it adjusts the stiffness ofthe beam spring 50 in a certain area along the longitudinal axis. Thebeam spring 50 may be made of various materials and/or combinations ofmaterials including composites, metal, in-cast metals, and plastic-metalhybrid materials. By incorporating supplemental stiffeners 140 made ofmaterials of various stiffness rates at various places in the crosssection and along the longitudinal centerline, one can vary thestiffness behavior of the spring as needed. For instance, the inclusionof a softer composite supplemental stiffener material along a length ofthe longitudinal axis of a beam spring with a constant cross sectionwill vary the stiffness along the beam spring, creating a softer areaalong the length of the longitudinal axis where the softer material islocated. Note that harder material may be used as a supplementalstiffener in the beam spring either separately or together with softermaterial, both being referred to as supplemental stiffeners in theinvention. Similarly, a metal or metals of varying stiffness rates maybe incorporated together to form a beam spring as well. In-casttechnology, over-forging and insert molding one metal into a cavitywithin another are several examples of this type of beam spring.Over-molding plastic onto steel frames, or hybrid metal plasticconstruction, can also be used to develop a beam spring with asupplemental stiffener.

FIG. 5 shows a beam spring 50 with a supplemental stiffener 140 havingmultiple cross sections. In this instance, the spring rate is varied notby changes in the outer spring cross section, but by changing the crosssection and thus the spring rate of the supplemental stiffener.

FIG. 6 shows a beam spring 50 attached to a chassis 20 at two points.This is a similar attachment method as is used with conventional leafsprings.

FIG. 7 shows a beam spring 50 attached to a chassis 20 at a singlepoint. This mounting method allows for more flexible packagingconsiderations and allows for a cheaper chassis 20 construction, withouta second suspension attachment point. The beam spring may be attached ina variety of ways. One way to attach a single point beam spring is toform the first end of the beam spring to cooperatively nest over anexisting leaf spring mount on the chassis. A hole provided in the beamspring, which matches that of the existing chassis mount, can be pinnedto fixedly attach the beam spring to the chassis i.e., a single chassiscould be used for both dependent and independent. Features on the beamspring can be incorporated to provide leverage against the chassis whenmounted with a pin in order to prevent rotation of the beam spring aboutthe fixing pin. In this way, a beam spring attached by a single pointcan elastically support a changing suspension load.

The beam spring may also be attached to the chassis at two points. Oneway to attach a dual point beam spring is to form each end of the beamspring to cooperatively nest over a corresponding, existing leaf springmount on the chassis, similar to the fashion described for a singlepoint beam spring above.

Another way of attaching a beam spring to the chassis includes a sleeveattached to the chassis, designed to slip over an end of the beamspring. The beam spring may then be pinned, glued or crimped to fixedlyattach it to the frame and prevent rotation of the end of the beamspring in relation to the chassis.

The attachment mechanisms and configuration of control arm or arms andthe shock absorber to the beam spring suspension are dependent on theparticular configuration and materials used.

Various other modifications to the present invention may occur to thoseskilled in the art. For example, the inclusion of halfshafts and asprung differential and/or transmission to the beam suspension system.Additionally, control arms with more than two attachment points may beemployed. Other modifications not explicitly mentioned herein are alsopossible and within the scope of the present invention. It is thefollowing claims, including all equivalents, which define the scope ofthe present invention.

What is claimed is:
 1. An automotive suspension beam spring comprising: a generally longitudinal spring body having a spring length and a longitudinal centerline, wherein said spring body is made from a spring material having a vertical spring rate constant in the vertical plane and a horizontal spring rate constant in the horizontal plane, further wherein said spring body is capable of substantial relative elastic deformation in the horizontal and the vertical planes respectively; an outer surface, said outer surface defined by at least one spring cross section taken perpendicularly with respect to said longitudinal centerline and having a maximum spring cross section width, wherein the ratio of said spring length to said maximum cross section width is at least 2; at least one supplemental stiffener, said supplemental stiffener further comprised of at least one other material with substantially different stiffness characteristics than said spring material, wherein at least one cross section of said supplemental stiffener is contained within said at least one cross section of said beam spring; further wherein said at least one supplemental stiffener further comprises a first cross section within a first segment along said longitudinal centerline of said spring body and at least one other cross section within another segment along said longitudinal centerline of said spring body, wherein said first cross section defines a first segment and said at least one other cross section defines a second segment, further wherein said first segment has a spring rate constant substantially higher than said at least one other cross section.
 2. An automotive suspension beam spring comprising: a generally longitudinal spring body having a spring length and a longitudinal centerline, wherein said spring body is made from a spring material having a vertical spring rate constant in the vertical plane and a horizontal spring rate constant in the horizontal plane, further wherein said spring body is capable of substantial relative elastic deformation in the horizontal and the vertical planes respectively; an outer surface, said outer surface defined by at least one spring cross section taken perpendicularly with respect to said longitudinal centerline and having a maximum spring cross section width, wherein the ratio of said spring length to said maximum cross section width is at least 2; further comprising at least one supplemental stiffener, said supplemental stiffener further comprised of at least one other material with substantially different stiffness characteristics than said spring material, further wherein at least one cross section of said supplemental stiffener is contained within said at least one cross section of said beam spring; further wherein said spring body is a metal with one crystal structure and at least one of said at least one other material is a metal with a different crystal structure.
 3. An automotive suspension beam spring comprising: a generally longitudinal spring body having a spring length and a longitudinal centerline, wherein said spring body is made from a spring material having a vertical spring rate constant in the vertical plane and a horizontal spring rate constant in the horizontal plane, further wherein said spring body is capable of substantial relative elastic deformation in the horizontal and the vertical planes respectively; an outer surface, said outer surface defined by at least one spring cross section taken perpendicularly with respect to said longitudinal centerline and having a maximum spring cross section width, wherein the ratio of said spring length to said maximum cross section width is at least 2; further comprising at least one supplemental stiffener, said supplemental stiffener further comprised of at least one other material with substantially different stiffness characteristics than said spring material, further wherein at least one cross section of said supplemental stiffener is contained within said at least one cross section of said beam spring; further comprising at least one inner chamber formed by an inner spring surface, wherein said inner surface is defined by an inner surface cross section, further wherein all of said inner surface cross section is contained completely within said at least one cross section of said spring body. 